Finding good programmer is hard, but even if there are good programmers within the interview candidates, it may still hard to recognize them. There is an article here on tips to explore their experience and tap into their skill to find out what they really worth. Tips like reading their code is actually the most useful among them:
… Josh Bloch suggested one technique we all seemed to like: Have the candidate bring a code portfolio to the interview. Look at the candidate’s code and talk to them about it. Although we were concerned that some candidates may not have code they could legally bring to the interview, we figured most candidates could probably come up with something. It can’t hurt at least to ask a candidate to bring to the interview a sample of code they had written in the past.
Josh Bloch: I want to see their code. You get to see what they pick. You learn what they value. You learn how they communicate…
I used this technique for interviewing software engineers and interns. Reading their code is like reading a piece of writing when hiring a technical writer. You see their work and their coding style. Have they commented the codes well? Have they tried to optimize their code?
How to Interview a Programmer – [Artima Developer]